1. Field of the Invention
The invention relates to a pneumatic vehicle tire for utility vehicles having a tread comprising circumferential grooves that run in the circumferential direction and divide the tread into circumferential ribs. An envelope that runs in parallel with the tread periphery in the tread and is in contact with the deepest circumferential groove or grooves from radially inside defines, together with the tread periphery and the shoulder-side edge sections, a tread gross volume and all the grooves in the tread define a groove volume.
2. Discussion of Background Information
A tire of the type mentioned in the introduction is known by way of example from U.S. Pat. No. 5,535,798 B. In order to achieve uniform tread wear, the tread is divided into circumferential ribs by four wide circumferential grooves that run in the circumferential direction. An additional narrow circumferential groove that runs in the circumferential direction is provided in the two shoulder-side circumferential ribs in the proximity of the edges of the tread. The wide circumferential grooves are defined by groove edge surfaces that are provided with depressions in the form of negative three-sided pyramids, whose peaks face the tread periphery.
In order to reduce the roll resistance of pneumatic vehicle tires, a plurality of measures have already been proposed, by way of example, a reduction of the profile depth or a reduction in the width of the tread. These measures are aimed at reducing the volume of rubber that deforms during the rolling motion. In addition, special tread compounds reduce the roll resistance, for example, tread compounds that comprise a comparatively small proportion of filler material.
A plurality of published patent applications and patents is concerned with the subject of reducing the roll resistance of utility vehicle tires in order to reduce the fuel consumption of a vehicle. It follows from this, that a tire for truck driving wheels is known, by way of example, from EP 0 973 652 B1. The tire comprises a tread that is divided into blocks in order to reduce the roll resistance and which blocks are laced in an axial manner by slots. In addition, the blocks are mutually separated by transverse grooves that are provided in each case with additional slots. In addition, a plurality of longitudinal slots is provided.
In the hitherto unpublished European patent application 09169199.8 of the assignee of the pending application, it is proposed in order to reduce the roll resistance to reduce the groove volume in the tread in favor of increasing the volume of rubber in the tread. The groove volume is reduced, by way of example, by virtue of the arrangement of narrower circumferential grooves or a comparatively smaller number of circumferential grooves. Contrary to the hitherto opinion of the scientific world, surprisingly it has been demonstrated that an increase in the volume of rubber in the tread noticeably reduces the roll resistance. It has been demonstrated that in the case of a comparatively small groove volume the rigidity of the profile in the radial direction is increased to such an extent that the deformation amplitude of the tread is reduced in a scale of magnitude that effects an over-compensation of the anticipated effect—an impairment of the roll resistance as a result of there being more available rubber. The roll resistance of the tire is consequently reduced. The reduction in the roll resistance that can be achieved in comparison to a tire embodied according to the prior art can be significant depending upon the proportion of the groove volume.
The length and the width of the ground-contacting surface area of the tire are only insignificantly changed by virtue of this aforementioned measure that improves roll resistance. The contact surface area between the tires and the road is increased in the case of a reduced groove volume but with an almost identical ground-contacting surface area. Consequently, the radial surface pressure in the ground-contacting surface area is reduced per unit of area. However, a high radial surface pressure is desired in the ground-contacting surface area in order, by way of example, to achieve a good tire handling in the case of different road surface conditions. When using a profile-based optimization of the roll resistance by reducing the groove volume, a conflict of aims can occur with regard to the tire handling.